Furnaces for molten mktal

ABSTRACT

1. A FURNACE COMPRISING A REFRACTORY BATH, TO HOLD MOLTEN METAL UP TO A GIVEN LEVEL, A HEAT-CONDUCTIVE CUPSHAPED REFRACTORY VESSEL SUPPORTED IN THE BATH IN AN UPRIGHT POSITION AND SPACED INWARDLY FROM THE WALL OF THE BATH, SO THAT MOLTEN METAL CAN SURROUND THE VESSEL IN THE BATH, SAID VESSEL HAVING AN UPWARDLY DIRECTED MOUTH ABOVE THE GIVEN METAL LEVEL AND CLOSED BY A DOWNWARDLY DIRECTED NOZZLE FOR PASSING A HIGH-VELOCITY STREAM OF HOT GAS FROM A FUEL BURNER DOWNWARDLY INTO THE MOUTH OF THE VESSEL, THE INNER SURFACE OF THE VESSEL FORMING A REVERSING BAFFLE FOR DOWNWARD IMPINGEMENT AND REVERSE FLOW UPWARD OF THE STREAM OF HOT GAS, AND THE VESSEL HAVING AN OUTLET FOR HOT GAS ABOVE THE GIVEN METAL LEVEL CONSTITUTED BY PORTS THROUGH THE RIM OF THE VESSEL.

April 8, 1975 i o. w. KING R0. 28,382

FURNACES FOR MOLTEN METAL Dtifliflll Filed July 22, 1969 2 SheBts-Shuat1 April 8, 1975 0, ng Re. 28,382

' FURNACES ma 510mm: 2.1mm.

Original Film; July 22, R369 '2 Sheets-Sheet 2 United States Patent Re.28,382 Reissuecl Apr. 8, 1975 28,382 FURNACES FOR MOLTEN METAL DavidWalter King, Solihull, England, assignor to Morganite Thermal DesignsLimited, Norton, Worces ter, England Original No. 3,635,457, dated Jan.18, 1972, Ser. No. 843,582, July 22, 1969. Application for reissue Jan.18, 1974, Ser. No. 434,629 Claims priority, application Great Britain,July 25, 1968, 35,500/ 68 Int. Cl. C2lc 7/00 US. Cl. 266-33 R 8 ClaimsMatter enclosed in heavy brackets [1 appears in the original patent butforms no part of this reissue specification; matter printed in italicsindicates the additions made by reissue.

ABSTRACT OF THE DISCLOSURE A furnace for molten metal comprises arefractory bath to hold metal surrounding a heater which consists of acup-shaped refractory vessel which stands in the bath and receives ahigh-velocity stream of hot gas directed into the mouth of the vesselfrom a fuel burner.

DESCRIPTION This invention relates to furnaces and provides a furnacesuitable for melting metal and holding molten metal ready for use, suchas in diecasting.

It is known to provide such a furnace consisting of a thermallyinsulated bath, to hold the molten metal, into which extends animmersion heater which may be an electrical heater or a conduit forflame from a fuel such as gas and air.

According to the present invention, a furnace comprises a refractorybath, to hold molten metal up to a given level, a heat-conductiverefractory vessel supported in the bath in an upright position andspaced inwardly from the wall of the bath, so that molten metal cansurround the vessel in the bath, said vessel having an upwardly directedmouth above the given metal level, and a fuel burner for producing ahigh-velocity stream of hot gas directed downwardly into the mouth ofthe vessel, the inner surface of the vessel forming a reversing baflle,for downward impingement and reverse flow upward of the steam of hotgas, and the vessel having an outlet for hot gas above the given metallevel.

It is an important feature of the invention that a stream of hot gas, asdistinct from flame, is used to heat the refractory vessel. The hottestpart of a flame from a simple burner is at some point within theboundaries of the flame which therefore has a diminishing temperaturegradient towards the outside. It is however possible to produce from asuitable burner, a high-velocity stream of hot gas more uniform intemperature than a flame and which can therefore, more efficiently thana flame, uniformly heat to a high temperature a body having a surfaceswept by the hot gas stream and particularly a vessel of which theinside surface forms a reversing baffle for the hot gas stream.

A gas-air burner suitable for producing a high velocity stream of hotgas is described in United Kingdom Pat. Specification No. 1,100,156 andsuch a burner is preferred for use with the present invention.

An open-mouthed refractory vessel suitable for use with the inventionmay be similar to, or actually consist of, a cup-shaped crucible such asis well known for holding molten metal in foundry work and which is madeof a refractory material of high thermal conductivity, such asclay-graphite.

The invention is illustrated, by way of example, on the accompanyingdrawings, in which:

FIG. 1 is a longitudinal section through a furnace,

FIG. 2 is a cross section on the line 11-11 of FIG. 1, and

FIG. 3 is a cross section similar to FIG. 2 but showing a modification.

The furnace illustrated by FIGS. 1 and 2 comprises a bath consisting ofa casing 1, which may be of metal or brickwork, having an intermediatelining 2, of a refractory, thermally insulating material such asdiatomaceous brick, and an inner lining 3, of a refractory materialresistant to molten metal such as a cast refractory.

As shown by FIG. 1, the bath has a sloping end forming an inlet 4through which are fed billets 5 of metal to be melted, a flap 6 beingprovided to close the inlet.

The top of the bath is closed, except for a ladling opening 7 and a flue8, by a cover 9 having intermediate and inner linings l0 and 11 ofmaterials similar to those of the linings 2 and 3. An inverted weir 12depends into the bath from the cover lining 11 down to below a normalmolten metal level X--X so as to close off the ladling opening 7 fromthe space above the metal level from which hot gases can exhaust throughthe flue 8. A part 9A of the cover is hinged to form an inspection door.

Above the center of the bath, the inner lining ll of the cover embodiesa downwardly directed nozzle 13 for a high-velocity stream of hot gas,from a high-pressure gas-air burner 14 mounted in the cover 9, to entera claygraphite, cup-shaped refractory vessel 15 mounted on a plinth 16on the bottom of the bath.

The vessel 15 is of such size that it has a surrounding clearance fromthe wall of the bath, to provide space for molten metal, and the mouthof the vessel 15 opens above the metal level and with an annularclearance around the nozzle 13.

The burner 14 is fed, through pipes 17, with air and gas under pressureso as to produce a high-velocity stream of very hot gas which impingescentrally at the base of the inner surface of the vessel 15 and isreversed, by the bafile effect of such surface, to sweep upwardly overthe surface and exhaust around the nozzle 13, over the surface of themetal in the bath and out through the flue 8.

The clay-graphite vessel 15, having a high thermal conductivity, becomesheated by the hot gas and transmits heat to the surrounding metal in thebath, the transfer of heat taking place very efliciently throughconduction and convection from the center outwards.

FIG. 3 shows a modified construction in which the rim of the vessel 15enters a groove 18 around the nozzle 13, which closes the mouth of thevessel 15, and a ring of outlet ports 19 for the hot gas is providedthrough the rim of the vessel 15. This arrangement enables the maximumrate of exhaust of hot gas from the vessel 15, and thus the heattransfer time, to be selected to conform to a designed optimum.

For convenience, the portion of the vessel 15 above the liquid level maybe referred to as the upper part of the vessel and the portion of thevessel below the liquid level may be referred to as the lower part ofthe vessel.

I claim:

1. A furance comprising a refractory bath, to hold molten metal up to agiven level, a heat-conductive cupshaped refractory vessel supported inthe bath in an upright position and spaced inwardly from the wall of thebath, so that molten metal can surround the vessel in the bath, saidvessel having an upwardly directed mouth above the given metal level andclosed by a downwardly directed nozzle for passing a high-velocitystream of hot gas from a fuel burner downwardly into the mouth of thevessel, the inner surface of the vessel forming a reversing baffle fordownward impingement and reverse flow upward of the stream of hot gas,and the vessel having an outlet for hot gas above the given meta] levelconstituted by ports through the rim of the vessel.

2. A furnace according to claim 1, in which the furnace has a cover, theburner is mounted in the cover and the cover has a refractory lining,part of which forms the downwardly directed nozzle for the stream of hotgas, leading from the burner into the vessel.

3. A furnace according to claim 2, in which the cover is provided with aladling opening and an inverted weir depending into the bath between theladling opening and the vessel.

4. A furnace according to claim 1, including a narrow foot supportextending between the bottom of the bath and the base of the vessel andspaced inwardly from the ball of the bath, such that molten metal cansurround the vessel and the bath.

5. A furnace comprising a refractory bath to hold molten metal up to agiven level, a heat-conductive cupshaped refractory vessel supported inthe bath in an up right position and spaced inwardly from the wall ofthe bath, so that molten metal can surround the vessel in the bath, saidvessel having an upper rim defining an upwardly directed month whichopens above the given metal level, a nozzle structure engaging at leasta portion of said rim of said vessel for passing a high velocity streamof hot gas from a fuel burner downwardly into the mouth of the vessel,the inner surface of the vessel forming a reversing bafile for downwardimpingement and reverse flow upward of the stream of hot gas, saidvessel comprising a lower part and an upper part, the lower part beinglocated below the said given level so as to be immersed in the saidmolten metal, said upper part being an upward extension of said lowerpart and comprising that part of the vessel above said given level, saidupper part comprising at least first and second portions, the firstportion comprising at least a section of the said rim, which section isin engagement with said nozzle structure, and said second portionincluding means defining at least a portion of an outlet means forremoval of said hot gases from the vessel out over the surface of themolten metal, and a flue means in said furnace spaced from said outletmeans for receiving said gas exhausting from said outlet means andpassing over the surface of the molten metal before discharging throughsaid flue means.

6. A furance as defined in claim 5 and in which the furnace has a cover,said cover being provided with a ladle opening and an inverted weirdepending into the bath and separating said ladling opening from saidoutlet means.

7. A furnace as defined in claim 5 and including an inlet through whichbillets of metal to be melted are fed into said furnace, said inletinclluding a slapping wall upon which said billets are placed and saidflue means being disposed such that said gases from said outlet meanspass over said billets before being exhausted through said flue means.

8. A furnace comprising a refractory bath to hold molten metal up to agiven level, a heat-conductive cupshaped refractory vessel supported inthe bath in an upright position and spaced inwardly from the wall of theboth, so that molten metal can surround the vessel in the bath, saidvessel having an upper rim defining an upwardly directed mouth whichopens above the given metal level, said rim engaging and beingsubstantially closed by a downwardly directed nozzle structure forpassing a high velocity stream of hot gas from a fuel burner downwardlyinto the mouth of the vessel, the inner surface of the vessel forming areversing baffle for downward impingement and reverse flow upward of thestream of hot gas, said vessel comprising a lower part and an upperpart, the lower part being located below the said given level so as tobe immersed in the said molten metal, said upper part being an upwardextension of said lower part and comprising that part of the vesselabove said given level, said upper part comprising at least first andsecond portions, the first portion comprising at least a section of thesaid rim, which section is in engagement with said nozzle structure, andsaid second portion including means defining at least a portion of anoutlet means for removal of said hot gases from the vessel out over thesurface of the molten metal, and a flue means in said furnace spacedfrom said outlet means whereby said gas exhausting from said outletmeans passes over the surface of the molten metal before dischargingthrough said flue means.

References Cited The following references, cited by the Examiner, are

of record in the patented file of this patent or the original patent.

UNITED STATES PATENTS 1,080,113 12/1913 Kugelgen et a1. 266-34 R2,152,446 3/1939 Temple 266-39 2,385,333 9/1945 Clapp et al 266-360 R2,496,113 1/1950 Wollner 126-360 R 3,211,546 10/1965 Kozma 266-33 R3,266,485 8/1966 Girton 126-360 R 1,751,533 3/1930 Taylor 126-360 R2,299,122 10/1942 Battin 126-360 R 2,587,078 2/1952 Wollner 126-360 R2,642,129 6/1953 Breese 126-360 R 2,603,476 7/ 1952 Whiston 266-33FOREIGN PATENTS 604,033 11/1945 Great Britain 266-33 R 961,175 6/1964Great Britain 266-33 R 35,500 7/1968 Great Britain.

GERALD A. DOST, Primary Examiner

